I should know the answer to this, but I don't

What is the restriction with putting muzzle attachments on an AK? I'm looking to put on a muzzle brake. It's an SAR-1, and I've got the folding stock already, if that makes a difference.

Thanks, all.

O Lord,
grant me the Serenity
to accept the things
I cannot change
the courage to change the things I can,
and the supreme firepower to make the difference.